1. Field
The present invention relates generally to aircraft and more particularly to attaching wings of an aircraft to a body for the aircraft.
2. Background
Final assembly of large aircraft is a complex procedure. The aircraft components are very expensive and have high inventory holding expenses. Further, the aircraft structural joints for attaching wings to a body are required to carry large loads. It is desirable to be able to quickly put together the different components of the aircraft to reduce the amount of time that different components are present in inventory. Thus, it is desirable to quickly assemble components with structural joints that are robust and reliable.
Currently, each major component, such as a wing or body, cannot be fully preassembled before final assembly of the aircraft to increase efficiency. This type of assembly of components allows for inspections and functional testing to be completed at the sub-assembly level. This type of testing includes, for example, leak testing of wing fuel tanks. When the testing of a component occurs before assembling the component with other components, any results that may require changes or replacement of parts can be preformed without disrupting the sequence in which the aircraft is assembled. This type of process saves time and reduces costs.
In attaching a wing to a body, older aircraft use one large pin for the front wing spar to body frame joint. This type of assembly facilitates quick assembly during manufacturing. This older approach, however, contributes to the weight of the aircraft. Although the use of a large pin for the wing front spar to body frame joint allows for preassembly of sub-assemblies and testing of those sub-assemblies prior to assembly, this approach has been changed in the current assembly processes used for aircraft to reduce the amount of weight.
Current manufacturing processes for aircraft attach the wings to the body using complex wing front spar to body frame joints. For example, wing front spar to body frame joints that use shear fasteners reduce the weight as compared to using a single pin joint. These types of joints, however, take considerable time to assemble and do not allow for functional testing of sub-assemblies, such as the fuel tanks in the wing, prior to final assembly. These types of joints incorporate many shear fasteners. These shear fasteners reduce wing weight as compared to using a pin. Further, shear fasteners efficiently carry flight loads between the wing and body.
This type of assembly process does not allow for complete assembly, preassembly and testing sub-assemblies, which results in additional work being performed in the final assembly. The attachment of the structural shear fasteners results in pressure areas or boundaries in the body or the wing being penetrated. For example, the fuel tank in the wing may be penetrated during this process. This approach is more expensive and disruptive if components fail tests in the completed aircraft. A result of this current approach is that the final fuel tank seal completion occurs late in the aircraft manufacturing cycle. Currently, the sealing of the fuel tanks are not completed when the wing is assembled. Instead, local portions of the fuel tanks are sealed during the wing-to-body assembly. Testing is then performed on the fuel tanks after the wings have been attached to the body. This sealing happens in the wing-to-body assembly because the shear fasteners are not attached until the assembly. The attachment of these fasteners could penetrate the fuel tanks within the wing. If problems are detected by the testing that require changing parts or modifying parts to properly seal the fuel tanks, the assembly process is interrupted to correct the problem.
As a result, other processes in assembling the aircraft may be delayed until the fuel tank is properly sealed. This situation results in increased time and costs needed to assemble the aircraft.